I beat the game.
It is cool and fun, I always enjoy this sort of catch and throwback bullet mechanics, and the variable rythm according to the beats of the music is an interesting twist which gives a real identity to the game.
One thing I did not like is the insane delay between two player shot with most weapons, the game almost feels unresponsive even if it's obvioulsy not and enemy hps are fixed accordingly, it made the game feel a bit worse than it should to me.
Very solid game anyway, congratulations.